Telephone system



March 13, 1928.

D. B. ROBISON TELEPHONE SYSTEM Filed May 17. 1924 DANIEL B. ROBISON, OF OICERO, ILLINOIS,

series.

AssrenoR 'ro KELLOGG SWITCHBOARZD AND SUPPLY COMPANY OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

Application filed May 17,

lily invention relates to telephone systems and has particularly to do with a private trunk or telephone line extending between a private or an executives ofiice and a distant or main exchange.

Prior to my invention it was the praclice, where a number of parties in the same suite of oiiices or same building receive and extend calls over the same trunk lines, to provide a private branch exchange at the suite of ofiices or building in which said trunk circuits terminate, the private branch exchange being attended to by an operator who attends to the calls and sets up the desired connections. It sometimes occurs that an executive or very busy party does not wish to talk with a certain other party who is calling him and the private branch exchange operator is instructed to first find out the name of the calling party and to inform the called for party the name of the calling party before the called for party will con-- sent to'talk with the calling party and if he does not wish to converse with the calling party, a diploi'i'iatic excuse will be offered by the private branch exchange operator to the calling party. The attending of such calls by the private branchoperator is found objectionable by some busy executives for various reasons, and they iind it more satisi'actm'y and obtain more privacy and secrecy it they are able to have their private secretary handle their calls personally instead of having their calls attended to by the private branch exchange operator. It is an object of my invention to provide a trunk circuit or private line extending from the main exchange to. the executives oflice over which the executive may converse directly with the calling party.

Another feature of my invention is the provision of a private trunk line extending from the main exchange to the executives private secretarys desk, which is operatively associated with the executives private trunk line. said trunk circuit being provided with means so that calls, extended from the main exchange over the executives trunk line, may lirst be attended to by the private secretary to ascertain the name ot'the call lug subscriber who will, after learning his name, effect operation of certain means in the executives trunk line to signal and coni-- (:retiy with the executive or called for party to learn whether or not he will talk 1924. Serial No, 713,879.

with the calling party and it he so wishes,

the private secretary will operate other means provided in thc executivos trunk line to connect theoxecutive or called torparty in conversational circuit with the calling party.

Another ieature of my invention is the provision of means in the executives trunk circuit, which when operated, will permit calls to be'roceived and extended directly over said trunk circuit independently of the private secretary.

A further feature of my invention is the provision of control means controlled by the executive or called for party for signalling to* a disconnection at the main exchange, said means also operable to maininane tain the called for subscriber in circuit with the calling party during conversation.

Still another t'eature of my invention is the provision of means for enablingthe private secretary to converse over his private trunk line with the mainexchange independently oi the excutivestrunk line.

The above features as well as others will be more specifically pointed out in the ensuing specification, reference being had to the accompanying drawingwhich illustrates two trunk circuits or private lines of my invention terminating at one end in terminals at amain exchange and terminating at the other end in substations of any well known common battery type, and associated with these two trunkcircuits or private lines is shown the private sccretarys trunk circuit and telephone set operatively associated with the said. two trunk circuits. The calling end of a well known operators cord circuit is also shown which'is adapted to be connected to any one of the trunk circuits appearing in the main exchange.

Referring now in general to my invention as illustrated in the drawing, C represents the callingend of a well known operators cord circuit, and comprises a calling plug GP, a ringing key BK for connecting the ringing generator G and battery B to said plug, a sleeve relay CS,'supervisory signal SS and a supervisory relay CT. A listening key L K is also provided for connecting the operators telephone set '(not shown on the drawing) to the tip and sleeve conductors of the cord circuit C.

Referring now to the trunk circuit or private line TC extending from the main exchange, this trunk circuit TC terminates at the main exchange in a jack J and terminates at its other end in a common battery subscribers substation Ex. No 1. a The trunk circuit TC comprises a cut oil" relay CU tor current flowing" over SfildrCOl'ltllLCtOlS to cause a signal- CL to light,;andto also operate" a: buzzer mechanism BU imthe private secretarys'trunlv ClLiYCtizlt PSTto sig'nab the private secretary. The private secretary upon being signalled \Vltlll operate a; two-way combination answering and talking key ATK in the trinrlc circuit TO by moving the same to the left whereupon the holding; relay HR will operateand bridge the holding coil I'IC across the conductors of thetrunk circuit TC to hold the relay CT in the cord circuitG energized. The private secretary upon. learning the name of the calling party and, the party wanted, and assuming it is the party at substation No. 1, will operate the: ringing key RK to connect and supply ringing current from the generator G to. the trunk conductors extending to said substation, and willalso operate the talking key TAK to enableher to converse secretly with theparty at substatiom Ext. No. 1. The: party upon responding wilt be intornied by theprivate secretary the name of the party calling and will ascertain-whether ornot the called for party will talk to the calling party and it, he so desires the operator will then operatethe key GK to cause relay CR to operateito connect the calling and called for parties in conversational circuit and r the private secretary will restore the talking key 'IlAK and thekey'ATK. A key OK is pro videdat the substation EX. No; 1 for pernut-ting the executive or party at said substation-t0 extend calls to the main exchange over the trunk circuit TC without the aid of the private secretary.

The privatesecretarys line PST comprises a jack J which is located at the inain exchange. together witha cut 01ft relay CO, Line relay LR and supervisory signal S, while at the private secretarys desk is a buzzer BU, a key BK for controlling the eineuitofi the buzzer BU, a relay RR, a calling lamp signel CL", and a listening key PLKv tot" connecting the private secreta-rys telephone. set 0 to the trunk circuit PST or to the trunk circuits extending to the different executives ofliees.

The trunk circuit vor private line TC termini) tes at" the main exchange and is provided with the same apparatus and has the same; circuitarrangement as the trunk circuit orprivate line TC and operates in the same identical manner, the same reference characters being used as those used in trunk circuit TC but having exponents aflixed thereto. a y a For a clearer understanding of my invention a detail description will nowlic given of its operation by tracing a -all from the main exchange to the executives substation Noulroven thetrunk circuit TC, it being assumed that this is the wanted party.

The operator at the main exchange will answer the call initiated with the answering end of the cord circuit C (not shown in the drawing) in the usual and well known manner to ascertain the wants at the calling suln scriber, and: upon learning that the wanted party is the executive at substation Ex. No.

1, will insert the-cabling plug GP oli the calling end oli cord circuit G into the jack .7 oil the trunk circuit on private line TC extendto' the suhstatioirlfix. No. 1,. whereupon the sleeve relay CS and: the cut off relay CO will: energize in series over at circuit traced from battery through the winding of the sleeve relay CS, normal contact 3 of ring} ing key RIC, sleeve contacts of the plug CP and jack .l, through the winding of the cut off relay CO to ground. The out .ofii relay CO- eimrg'izing over this circuit closes its atternate contactst and 5, thereby removiuu the line relay LR and supervisory signal a from the trunk circuit TR- 'lheoperator at the main exchange will, after inserting the calling. plug GP into the jack J as just described, operate the ringing; key K to apply generator current to the trunk circuit 'IlG from the generator- G to cause the relay RR at the trunk circuit T6 to operate. The circuit for the relay RR may the traced from around through the generator G; alternate content 6 of the ringing key BK, tip contacts of plug CP and jack J, alternate contact 4: of relay CO, conductor 1 through the condenser a, winding of relay RR, conductors 'Z and 2. alternate contact 5 of relay CU, and through the winding? of relay C0 to ground-M Relay CO will not (lo-energize upon the opening of normal contact 3 of the ringing key Elias the alternate contact 3 of said key RK will be closed thereby couuecting battery to the sleeve contact of the plug GP so long the ringing key RK is in ilsoll norlual or operated position. Relay RR oh the trunk circuit TCwill be operated by current flowing over the circuit just tracedl aind \VllhfilOHO its alternate contacts 8 and 9 and" theclosing of its alternate con tact 8 estal'ilishos a circuit for the buzzer BU provided in the private secrctarys trunk circuit PST, which circuit may be traced from battery through the normal contact of" the buzzer control key BK, tbrouuh the buz zer BU, conductors 10 and 1]. and to gromut through alternate contact 8 of relay RR. 'llhe: buzzer BU will operate over this circuit ill:

llh

ill

to indicate to the private secretary that a call has been initiated and that her services are required. Theclosure of alternate contact 9 of relay RR closes a circuit for the calling la-i'np CL which will light to indicate the trunk line or private line over which a call is coming from the main exchange and the private secretary, upon hearing the buzzer EU and observing the lighted calling signal CL, will operate the twoway combination answering and talking key ATK to the left to closealternate contacts 12, 13 and 14; and the closing of alternate contacts 13 and 1-l connects the private secretarys telephone set to the conductors 1 and 2 of the trunk circuit TC to enable her to coininunicate with the calling subscriber or party. The circuit by which the private secretarys telephone set C is connected to the talking conductors of the trunk circuit TC may be traced from one side of the telephone set C. conductor 15. normal contact 16 0f the listening key PLK. conductor-.17. upper normal contact ofthetalking key TAK, through the condenser c and the alternate contact 13 of key ATK, to conductor 1 of the trunk circuit TC, and over the tip side of the cord circuit C, through the calling substation. back over the sleeve side of the cord circuit C at the main exchange, conductor 2 of trunk circuit TC, condenser 0 alternate contact 14 of key .ATK. condenser. a, lower normal. COHtaCt'Oif key TAK, conductor 18, normal contact 19 of key PLK, conductor 19. to the other side of the telephone set C. The private secretary converses over this circuit and inquires the wants and the name of the calling party. 'hen the key ATK is moved to the left and alternate contact 12 is closed as described above, a circuitis established for the holding relay HR traced from battery through the upper winding of said relay HR to ground. through the alternate contact 12 and relay HR energizing over this circuit closes its alternate contacts 20 and 21. The closure of its alternate contact 20 bridges the holding coil HC across the conductors 1 and 2 of the trunk circuit TC thereby establishing a holding circuit for the supervisory relay CT of the cord circuit C to prevent the restoration of said relay CTt-hercby preventing the lighting of the supervisory signal SS of the cord circuit C to avoid a false disconnect signal. The circuit for relay CT may be traced from battery through the Winding of relay CS. normal contact 3 of key RK, sleeve contactsof plug CP and jack J, alternate contact of relay CO. conductors 2 and 7. through the winding of the holding coil HC, alternate contact of the holding relay HR. conductor 1, alternate contact 4 of relay CC, tip contacts of the jack J and plug Cl normal contact 6 of key RK, alternate contact 23 of relay CS, through the winding key RBI to signal the subscriber or executive at substation Ex. No. 1 which has been as sumed to be the calledtor party, the circuit for the ringing current for signalling the party at the substation EX. No. 1 being traced from ground through the generator G, upper alternate contact of the ringing key RK, tip conductor of trunk circuit TC, through the call bell at the said substation EX. No. 1, to ground through the lower alternate contact of key RK. The private secretary will also throw herlistening key TAK associated with the trunk circuit TC thereby opening the normal contacts ofsaid key TAK to place her telephone set C out of circuit with the calling party and will close the alternate contacts of said key to connect her telephone set in circuit with the substation Rx. No. 1, whereby the private secretary enabled to secretly converse with the executive or party called for at substation EX. No. 1 without beingheard by the calling party, and the private secretary will now ascertain from the called for party whether or not he desires totalk with the calling party. Talking battery for the private secretary and called for party is provided from battery through the windings ot the battery feed relay BR and through the alternate contacts of key TAK to the talking conductors of trunk circuit TC.

Assuming now that the called for party wishes to converse with the calling party the private secretary will operate the key CK thereby establishing a circuit tor the connecting tlnoughrelay CR, traced from battery through the winding of saidrelay CR, to groundthrough alternate contacts 01 said key CK. Relay CR will energize over this circuit and close its alternate contacts 27 and 28: in the talkingconductors oi. trunk circuit TC thereby connecting the called for subscriber at substation EX. No. 1 in conversational circuit with the calling subscriber. Relay CR upon energizing also closes its alternate contact 29 thereby closing a lock ing circuit for itself which may be traced from battery through the winding oi said relay CR, alternate contact 29, conductor 30, to ground through alternate contact 21 of the holding relay HR. The private secretary now restores the key ATK and the key TAK to normal whereupon the private secretarys telephone set C is operatively disassociated from the trunk circuit TC. Upon the restoration of the key ATK the circuit through the upperwinding of theholding ill relay HR is opened at alternate contact 12 of. said keyATK but relayHR will not dc energize at this time, as a holding circuit is established for the same which maybe traced from battery throughthewinding of relay GS of cord circuit C, normal contact 3 of key BK, sleeve contactsot the plug GP and jack J, alternate contact 5 of relay CO, conductor 2, through the lower winding of the holding relay HR, alternate contact 28 of relay CIltlower normal contact of key RK, through? the now closed alternate switchhook contacts at-the substation Ex. No. 1, upper normal CODtiPCl'rOzl key RK, alternate contact 27 of relay CR, conductor 1, alternate contact 4; of relay CO, tip contacts of the jack .1 and plug. CP, normal contact 6 of key RlQ'alternate contact 23 of relay OS, to ground through the winding of the relay CT of. the cordcircuit C. Relay HR remains: energized over this circuit thereby maintaining itsaliternate contact closed to retain the holding coil HO bridged across the conductors of: the trunk TC, and also maintains its alternate contact 21 closed to maintain the locking circuit for relay OR. Thus, itwill; be readily apparent that the holding relay HR is controlled by the party at the StlbStiltlOllEX. No. 1 and it will also be seen that the relay CT at the cord circuit 61 is under the control of the called for party at said substation so that the supervisory disconnect signal SS is controlled by the said called for party.

Assuming now that the calling and called parties have terminated their conversation the calling party will: replace his receiver upon its switchhook thereby operating well known means in the answering end of the cord circuit C to signal for disconnection in'the well known manner, and the called for subscriber at the executive substation Ex. No. 1 will replace his receiver; and upon the replacement of his receiver upon its switchhook, the holding circuit for tl1e-l1olding relay HR will be opened whereupon said relay HR restores to normal and opensy its alternate contacts 20 and 21-, thereby openingthe lockingcircuit; for the relay CR which: will now restore to normal, and the opening of alternatecontact 20 of the relay H-Rf-opens the circuit for the relay CT of the cord circuit C whereupon the saidrelay O'll restores to normal to close the circuit of the supervisory signal SS, which circuit may be traced from battery through the said signal SS. alternate contact 24 of relay OS, to ground through normal contact 25 of relay CT. The operator at the main exchange observing the lighted supervisory signal in the answering end of the cord circuit O and the lighted signal SS in the calling end of the cord circuit C will know that conversation has terminated and will with draw the plugs oat cord circuit C from their respective jacks whereby the eordwcircuit G will restore to normal in the well known manner; The withdra -a'l of the plug CP from thefljack J disconnects battery from the sleeve contact of the jack vJ thereby permitting the cut off relay CO to restore to normal to again place the line relay LR in circuit with the conductors l and ot the trunk circuit TO. The key CK is not a self locking key and therefore will restore immediately upon the private secretary removing her finger therefrom. The trunk circuit TC is now in its normal position and ready for other calls.

Assuming now that the party at the cxcutivels substation No. 1 desires to initiate a call through the main exchange, the party will do sohy first removing the receiver from its switchhook and will then operate his calling key OK which will close an energizing circuit for theholding relay UR tI'tICQdxfLOm battery through the upper winding of said relay HR, conductor 33a to ground through the alternate contact 34. of said key OK; and will alsoclose a circuit for connecting through relay GR traced from battery through the winding of said relay CR, conductor 35, to ground through alternate contact 360i the keyOK. The key OK is not a locking key and will restore upon the removal of pressure from it. whereby its alternate contacts-34 and 36 willopen but relay CR will not-deenergize when the contacts 36 of key OK are opened as a locking circuit is closed through its alternate contact 29, conductor 30, and the alternate contact 21 of relay HR to ground. Neither will relay HR (lo-energize when alternate contact 3% of key OK isopened, as a holding circuit is closed through its lower winding. The holding circuit for relay HR may be traced fronrhattery through: the winding of the line relay LR, normal contactfi of the cut oil relay CO, conductor 2. lower winding of relay HR, alternate contact 28 of relay CR lower normal contact of the key RK, through the now closed alternate switchluiok contacts of substation Ex. No. 1, upper normal contact of key RK, alternate contact 27 of relayOR, com'luctor L, to ground through normal contact 4: of the cutoft; relay CO. Relay LR will energize over this circuit and close its alternate contact thereby closing a circuit through the supervisory signal S to indicate to the operator at the maincxchangc that a call has been extended and that her services are required, whereupon she will take the answering plug of the cord circuit, C (said answering end however not hcingshown on the drawing as its operation is well known) and insert the same into the ack J thereby closing a circuit through the cut off relay CO of the trunk circuit TC in the well. known manner, and the cut-oft relay O0 energizing opens its normal contacts 4 and 5 therebyopening the circuit of the line relay LR which will now restore and also opensthe circuit of the slow-acting holding relay HR but the relay HR will not tie-energize as the circuit will now extend through the alternate contact 5 of relay CO and over the sleeve conductor of the cord circuit C to battery instead of through the winding of relay LR to battery. The holding relay HR is made slow acting so that the same will not tie-energize while the armature is moving from the normal contact to the alternate contact 5 of the cut-off relay CO thereby preventing the restoration oi? the relay CR. The operator at the main exchange will now inquire the wants of the calling party at the substation EX. No. 1 and will take care of his wants in the well known manner.

l pon termination of conversation the calling and called parties will replace their receivers, and the replacing o'l thereceiver at the called for substation at the'main exchange will bring about the lighting of the supervisory signal in the cord circuit C as will be well understood from the foregoing description, and upon the replacing of the receiver upon its switchhook at the calling substation Ex. No. 1 the holding circuit'for the holding relay HR- will be opened at the alternate switchhook contacts of the said substation EX. No. 1 so that said relay HR will deenergize and open its alternate con t acts Q and 21 thereby causing the answering supervisory signal in the answering end oi the cord circuit C to light and also open the circuit of the relay CR of the trunk circuit TC which relay CR will restore to normal. The operator at the main exchange observing the lighted answering and calling supervisory signals will known that convcrsation has terminated and will take down the connection and upon the withdrawal of the answering plug from the jack Jot the trunk circuit TC cut off relay CO will deenergizc and connect the line relay in circuit with the conductors of the trunk circuit- TC. The trunk circuit TC is now restored to norinal and ready for other calls.

Assuming now that the executive or party at the executives substation EX. No.1 wishes to receive calls without having the same attended to by the private secretary, the private secretaiy will throw the two-way key ATK to the right which key will remain in this position until restored manually, said key when moved to the right closes alternate contacts 38 and 39 whereby the trunk talking conductors l and 2 are cut through from the jack J to thesubstation his. No. 1 exclusive of the relay CR. Now when. a call is extended from the main exchange, upon the insertion of the plug CP into the jack J and when the ringing key BK ot the cord circuit C is operated :as'described above, ringing current will be ap plied to the call bell of the substation Ex. No. 1 to signal the called for subscriber over a circuit traced from ground through the generator (3i, alternate contact 6 of key RK, tip contacts of the plug CP and jack J, alternate contact l of relay CO; tip conductor of trunk circuit TC alternate contact 38 of the key ATK (it being remembered that thecontact 3 oi? the ringing key BK as is set forth in the foregoing specification. Upon the response of the called for party at substation Ex. 1T(). 1, a circuit is established for the relay CT of the cord circuit C which will operate to open its normal contact 25 thereby preventing the lighting of the super-. visory signal SS, said circuit for relay CT being tracedzlrom battery throughthe winding of the relay CS normal contact 3 key BK, sleeve contacts of the plug CP and jack J, sleeve conductor of'trunk circuit TC, al-

ternate contact 39 of key A-TIQloWer normal contact of key BK, through the now. closed alternate switchhook contacts of the substation EX. No. 1, upper normal contact of key RK, alternate contact 38 of key ATK, tip conductor of trunk circuit TC, alternate contact 4 of cut-off relay CC, tip

contacts of the jack J and plug CP, normal contact 6 of key RK, alternate contact 23 of relay CS, to ground through the winding of relay CT. Relay CT energizing over this circuit opens its normal contact thereby opening the circuit of the supervisory signal SS. Conversation is also carried'on through the substation EX. No. 1 over this same part of the trunk circuit TC as just traced. lVhen conversation hasterminated the calling party replacing his receiver upon its switchhook, operates the signal atthe answering end of the cord circuit, and the party the substation Ex. No. 1 upon replacing his receiver upon its switchhook opens the circuit of the relay CT of the cord circuit C, whereupon said relay CT restores to normal and closes its normal contact 25 thereby closing a circuit for the supervisory signal SS. The operator at the main exchange observing the lighted supervisory signals will know that the conversation has terminated and will withdraw the answering and calling plugs from their respective jacks,whereupon the cord circuit C'restores tonormal, and the removal of the plug CB from the jack .5 will "permit the cutloft re layLC.O:t0 restoreto nonmalrthus rendering the trunk circuit TG iavailable vfor other calls.-When the :key ATK is thrown to itsfrom battery through the cwinding of the line relay LR, normal centric-t5 ofrelayCO, sleeive conductor of trunk circuit TC, alternate'contact 39 ot key ATK, lower normal contact of-ikey iRK', through llllCTlOWl alternate switch'hook :contacts of the substation EX. No; .l upper normal contact of keyRK, alternate contact 38 of key ATK, tip condoctor oftrunk circuit TC, through the normal contact 4 o firelay CO to ground. The line relay energizing over this circuit will close its alternate contact, thereby causing the SighalSto light to'notify the operator at .the main exchange that a call is awaiting her attention whereupon she wan take'care of the call in" the manner as described above. Therprivatesecretary may conversewitih a party-attire main exchange exclusive of the trunk circuit TC or TC-=by operating her listening key PLK, whereby her telephone set l) will be disconnected from the trunk circuits PG and TC; Assuming that a party at themainpexchange desires to talk with the private secretary, the operator at .the main exchange will insert the calling plug C1 into the jack thereby closing-a circuit for the sleeve relay CS and cut-off relay C0 astol'lows: battery through the winding of relay CS,nonn1al contact 3 of key BK, sleeve contacts of the plug GP land jack J, through the winding of relay CO toground. Relay CQWripou. energizingwill close its alternate contacts 50 and 51 thereby removing the line relay LR from the control of the telephone set 0. The operator at the mainexchungc upon inserting the plug-GP into the jack :J willoperate her ringing key RK to connect generator current to the trunk circuit PST over acircuit traced from ground through the generator G,- altcrnate contact 6 of key BK, tip contacts-0f plug GP and jack J, through the alternate contact 50 of relay CO, condenser 0, through the winding oi rela yRR, alternate contact 51 of relay CO and through the winding of said relay CO to ground. Relay RR will operate over thisvcircuit and close its alternate contactii3 to cause the signal CL to light and 1 ,oea, me

relay RR will also close its alternate coir tact 5410 close a circuit from ground through the buzzer EU and buzzer key BKlo ha t. tery. The buzzer EU will operateto attracl the attention-of the private secretary or attendant, who, upon observing the lighted signal CL, will know that a call has been extended to her private trunk line PST and she will operate her listening key PLK to open normal contacts 16 and 19 and close alternate contacts 16 and 1!) to connect her telephone set to the talkin conductors of the trunk circuit Pll'l andwill converse with theicall ing party. During the application of ringing current, cut-oil relay CO remains energized as 'hutlcrywill be connected in circuit. with said relay C0 through the :iltcruate contact am the ringing key RK. Upon the removal of the receiver at the private score tarys telephone set 0 and the throwing oi the listening key PLK to its alternate position a circuit is closed For the relay CT of the cord circuit C, said circuit being traced from bath-aw through the winding of the relay CS, normalcontact 3 orl' ringing key BK, sleeve contacts of libeplug CPand jack J, alternate contact 19 of key PLK, conductor 19, through the now elosedalternatc switchhook contacts of the telephone set 0, conductor 15, alternate contact 1(3 of the h'eylLK, alternate contact 50 0i the relay CO, tip contacts oi lhc sleeve J and plug GP, normal contact ('3 of key BK, alternate contact- 5313 of relay (15,10 ground through the winding ofrclay C'l.- Relay C'l energizing over this circuitopcns its normal contact thereby ell-arcing the siu'icrvisorysignal Upon terminationo l conversation, the private sceretury will replace her receiver upon its switc'hhook thereby op'eningthe circuit of the relay -C'.-l,'said relay CT (lo-energizes and closes its normal contact 25 to cause the ligbl ing'o t the supervisory relay to signal for a disconnection. The operator at the main exchange will upon observing the lighted suicrvisory signals in the cord circuit C withdraw the plug CP from the jack J thereby opening the circuit for cutoff relay G0 which will now restore to normal and connectibe line relay LR in circuit with the talking conductors of the private secretary's trunk lines PCT, and the relay CS of the cord circuit C will restore and open the circuit of the supervisory signal SS.

Assuming now that the private sccrctnr wishes toextend a. call to lhe main exchange. she will throw her listening key PLK to its alternate;position thereby disconnecting her telephone setO from the trunk circuits 'lC and "TC" 'and will connect the same to the talking conductors of the trunk circuit PST, to close a circuit for the line relay LR. traced from battery through the winding of said relay LR, normal contact 51 of relay CO, alternate contact 19 of the listcninglrcy Stl Hill

PLK, through the now closed alternate switchhook contacts of the telephone set 0, alternate contact 16 of the listening key PLK, to ground through the normal contact 50 of the cut-ofi' relay CO. Relay LR ener gizes over this circuit and closes its alternate contact thereby closing a circuit for the supervisory signal S, which signal S will light to indicate to the operator .at the main exchange that a call has been extended and that her services are required, whereupon she will insert the answering plug of a cord circuit into the jack J, thereby causingthe energization of the cut oil" relay CO, and relay CO energizing opens its normal contacts 5t) and 5t thereby removing theline relay LR from the trunk circuit PST.

After the conversation has terminated the private secretary will restm-e her receiver upon its switchhook and will also restore her listening key PLK, thereby opening the circuit oi the supervisory relay in theanswering end of the cord circuit at the main exchange whereiujion the supervisory relay Will restore and cause'the operation ot a supervisory signal to signal for a disconnection in the well known manner. The operator at the main exchange will now withdraw the answering plug of the cord circuit C from the jack J", whert-zupon the cut oii re lav Ct) will restore to normal and connect the line relay LE to the trunl: circuit Pt i'l. The trunk circuit PST is now in its normal position. a g

The trunk circuit TC operates in the same manner as trunk circuit TC and the operator at the main exchange will insert a plug of a cord circuit into the jackJ and the call will. be handled in the same manner to signal a party at. the executives substation Ex. N o. 2 as described. above in cormection with the trunk circuit TC.

As many trunk lines, as are be attended to by the private secretary by associating the same with the private secretarys telephone set and trunk circuit PST in the same manner inwhich the trunk circuits TC and TC are associated therewith.

Although I have illustrated and described a preferredv circuit arrangement of my invention, it is to be understood that I do not wish to be limited to the exact circuit arrangemcnt as shown and described, as changes and modifications will readily suggest themselves to those familiar with. the art, but that I'claim all that which may come within the spirit and scope of the appended claims.

WVhat I claim as new and desire to secure by United States Letters Patent, is:

1. A telephone system including a trunk circuit terminating atone end in a jack terminal at a main exchange and at its other end in a subscribers substation, an attendants trunk circuit terminating in one end desired, may

at said ma n exchange and at its otheriend in a telephone set, signal means for said attend ants trunk circuit for signalling the attend ant at said attendants trunk circuit, means er tor disassociating said substation and said main exchange and for signalling for a disconnectiini at the main exchange, and means for said trunk circuit :lor permitting calls to be extended from the main exchange to said substation exclusive of the attendant.

A telephone system including a trunk circuit terminating atone end in a main exchange and atits other end in a subscribers substation, an attei'idants circuit terminating in said exchange, a telephone set, signal means for said attendants circuit torsignah ling the attendant,means for said trunk circuit controlled from the main exchange for controlling said signal means, means for said trunk circuit for connecting said telephone set to said trunk circuit to enable the attendant to talk to the main exchange, means for enabling the attendant to talk secretly over said trunk circuit with a party at said substation, automatic means for (.lisassociating said substation and'said' main exchange and for signalling for a disconnection at the main exchange, said :mtomatie means controlled hy the party at said substation, and means for said trunk circuit for permitting calls to be extended from the main exchange to said substation exclusive of the attendant.

3. A telephone system including a trunk circuit terminating at one end in a main exchange and at its other end in a subscribers substat on, an attcndants circuit tern'iinating in'said exchange, a telephone set, signal means tor said attendants circuit for signal- -ling the attendant, means for said trunk circuit controlled from the main exchange for controlling said signalmeans, means for said trunk circuit for connecting said telephone set to'said trunk circuit to enable the attend ant to talk to the main exchange, means for enabling the attendant to talk secretly over said trunk circuit with a party at said substation, means forconnecting said substation through in conversational circuit with said n'iain exchange, automatic means controlled by said substation :tor disassociating said. substation and said main exchange andfor signalling for a disconnection at the main exchange, and means for said trunk circuit tor permitting ails to be extended from the main exchange to said substation exclusive ot the attendant.

4. telephone system including a main exchange, a distant subscribei."s substation, a

connecting circuit for interconnecting said substation and said lmain exchange, autofora disconnection :at the main exchange, an

lit)

attendants telephone set, :a connecting circuit for interconnecting said telephone set and a said main exchange, signalling means iorsaiid second connecting circuit for signalling thev attendant thereat, said signalling means controlled i via said first connecting circuit, and meansl'or said connecting circult for permitting calls to be extended from the main exchange to :the substation exclusire of the attendant.

5. iiArtelephone .systeni including a m ain exclmnge, a distant snbscribers substation, a connecting circuit for intenconnecting said substation and said main exchange, automaticmeans controlled bythe party of said substation for disassociating said substation and said main exchange and for signalling for axdiscoimection at the main exchange, an" attendants telephone set, a connecting circuit for interconnecting said telephone "and said main exchange, signalling means for said second connecting circuit for signalling the attendant thereat, said signailing means controlled viasaid first connecting 'ci rmit, means for said first connecting circuit for permitting the attendant. to talk secretly to either the main exchange or the subscriber at said substation, and means'itor said first connecting circuit for permitting calls to be extended from the main exchange to the subscribers substation exclusive of the attendant. y

*GQA telephonesystem including a main exchange, a distant subscriberssnbstation, a connecting circuit for interconnecting said substation and said main exchange, an at tendants telephone set, a connecting circuit for interconnecting said telephone set and said main exchange, signalling means for said second connecting circuit for signalling the attendant thereat, said signalling means cont-rolled via said first connecting circuit, means for said first connecting circuit for permitting the attendant to talk secretly to either the main exchange or the subscriber at said substation, means controlled by the attendant for connecting *said subscribers substation in conversational circuit with said 1 main exchange, automatic means controlled by said subscriber for disassociating said substation and said niainxexchange and for signalling tor a disconnection at the main exchange, and means for said connecting circuit for permitting calls to be extended frointhe main exchzu ge to the subscribci"s substation, 'exclusive of the attendant.

7. A telephone system including a main exchange, a subscrfi-befs substation, a connectingcircuit for interconnecting said substation and-said main exchange, a primate secretarys telephone set, aneans for said connecting circuit for permitting the placate secretary to converse with the main exchange, means for permitting the private sem'etary to secretly converse with the party at said substation, means for said connecting circuit for connecting said substation in conversational circuit with said main exchange, automatic means controlled by said subscriber for disassociati ng saidsu'bstation and said main exchange and for signalling for a disconnection at the main exchange, and means for said connecting circuit lor permitting calls to be extended from the main exchange to the subitation exclusive of the private secretary.

8. A telephone system including a main exchange,,a subscribers substation, a connccting circuit for interconnecting said substationiand said main exchange, a private secretarys telephone set. means for said connecting ci rcuit for permitting the private secretary to converse with the main exchange, aueans torpcrmitting the private secrete ry'to secretly converse with the party at said substation, means for said connecting circuit for connecting said substation in conversational circuit with said main exchm-age, automatic means controlled by said substation for automatically disassociating said substation and said main exchange and for signalling for a disconnection at the main exchange said means being operable toanaintain said subscribefls substation in a conversational circuit with said main exchange, and means for said connecting circuit for permitting calls to be extended from the main exchange to the substationfexelusive of the attendant.

"9.A telephone system including a main exchange and a Sl1l.)SCIll)G1"S substation, a link circuit for interconnecting the same, an attenda'nts link circuit, signalling means for said second link circuit. for signalling the attendant thereat, (means for said first link circuit for controlling said means, means for said first link circuit for permitting the attendant to converse with the main exchange via saidfirst link circuit, means for permitting the attendant to converse secretly with the subscriber at said substation, means for said first link circuit for operatively connectingsaid substation "in conversational circuit with the main exchange, automatic means controlled by said subscriber for dis associating said substation and said main exchange and for signalling for a disconnection at the main exchange, and means for the saidlink circuit for extending calls from theinain exchange to the substation exclusive otzthe attendant.

10. A telephone system including a main exchange and afisubscribefis substation, a link circuit for interconnecting the same, an

attendants link circuit, signalling means for said second link circuit for signalling the attendant thereat, means for said first link circuit for controlling said means, means for said first link circuit for permitting the attendant to converse with the main exchange via said first link circuit, means'tor said connecting circuit for permitting calls to be extended from the main exchange to the substation, exclusive of the attendant, means for permitting the attendant to converse secretly with the subscriber at said substation, means for said first link circuit for operatively connecting said substation in conversational circut with the main exchange, and automatic means controlled by the sub scriber at said substation for operatively disassociating said substationand said main exchange and for sgnalling for a disconnectionat said main exchange.

11. A telephone system including a main exchange and a subscribers substation, a link circuit for interconnecting the same, an attendants telephone set, means for permitting the attendant to talk over said link circuit with the main exchange, means for permitting the attendant to talk with a party at said substation secretly exclusive of the main exchange, means for said link circuit for connecting said substation and said main exchange in conversational circuit, means for said connecting circuit for permitting calls to be extended from the main exchange to the substation, exclusive of the attendant, and means located at said main exchange controlled by said substation for disassociating said substation and said main exchange and to operate disconnect signalling means at the main exchange, said means being operable to maintain said subscribers substation in a conversational circuit with said main exchange.

12. A telephonesystem including a main exchange and a subscribers substation, a link circuit for interconnecting the same, an at-tendants telephone set, means for said link circuit for permitting the attendant to con verse secretly with a subscriber at the main exchange and to converse secretly with a party at said substation, means in said link circuit whereby the subscriber at the said substation can call the main exchange without the assistance of the attendant, and means for said link circuit controlled by the attendant for connecting said substation in conversational circuit with said main exchange, said means controlled by the subscriber at said substation for discontinuing the conversational circuit and for signaling for a disconnection at the main exchange.

13. A telephone system including a main exchange and a subscribers substation, a connecting circuit for interconnecting the same, an attendants telephone set operatively associated with said connecting circuit, and means for said connecting circuit for permitting calls from the main exchange to be extended by the attendant to said substation, means for said connecting circiut for permitting calls to be extended from the main exchange to said substation exclusive of the attendant, and means for said'link circuit controlled by said substation for operatively disassociating said substation from said main exchange and for signaling 'for.

a disconnecting at the main exchange.

it. A telephone system including a main exchange, a plurality of subscribers substations, individual connecting circuits for interconnecting said substations and said main exchange, an attendants link circuit terminating at said main exchange, signal means for said link circuit for signalling the attendant thereat, individual means for each of said connecting circuits for operating said signal means when connection is made with any one of said connecting circuits and generator-current is applied thereto from said main exchange, means in said connecting circuits for permitting calls to be extended terminating in said main exchange, an at-c tendants connecting circuit terminating in said main exchange, means in said connecting circuits for permitting calls to be extended "from the main exchange to any of the subscribefis substations exclusive ot the attendant, signal means for said attendants connecting circuit for signalling the attendaut thereat upon a connection at said main exchange with any one of said connecting circuits, automatic means controlled'by the party at said substation for disassociating said substation and said main exchange and for signalling for a disconnection at the main exchange, and an individual supervisory signal for each of said connecting circuits for notifying the attendant the particular connecting circuit connected to at the main exchange 16. A telephone system including a main exchange and a plurality of subscribe-rs substations, trunk circuits for interconnecting said substations and said main exchange, an attendants telephone set, a trunk circuit for interconnecting said telephone set and said main exchange, automatic means controlled byi the party atsaid substationfordisassoci'ating'sai substation and saidmain exchange and for signalling for a disconnection at the main exchange, signal means for said trunk circuit for signalling the attendant thereat,means in said first trunk circuits for permitting calls to beextended to the substations. exclusive ofuthe attendant, and means for operatingsaid signal means from saidmain exchange via said trunk circuit or yia anyone of said trunk circuits.

17. A telephone system includin a main exchange and a plurality:of subscribers substations,trunk circuits for interconnecting said substations and said main exchange, automatic means controlled byi the party at said suibstation fondisassociating said substation and said main exchange and for signalling'for adisconnect-ion at the main exchange, an attendants telephone set, a trunk circuit for interconnecting said telephone set and saidinain exchange, signal means for said trunk circuit for signalling the attendant tliereat, means ,in said firsttrunk circuits for permitting calls to be extended to any or allo f "the substations exclusive of the attendant, means for operating said signal maelstrom said main exchange 'via said trunk circuit or vi'a 'any one of said trunk circnits,and n eans controlled by the attendant for permitting lierlto talk to the main exchange over thetrunk circuit over which said signal is operated. l

18. A telephone system includinga main exchange and a plurality of subscribers substations, trunk circuits for interconnecting said substations and said main exchange, automatic, means controlledfbythe party at said substation fordisassociating said substationand saidmain exchange and for signalling for fa disconnection at the main exchange, an attendants telephone set, a trunk,

circuit for interconnecting said telephone set and saia'niaia ea1mnge, signal means for said trunk circuit for si nallingthe attendant thereat, nie'ansin saidfirst trunk circuits perr'nitting calls to be extended from the "main exchange to any of the substations exclusive of the attendant, means for. operatsta is;

ing said signal means from said main exchange yiasaidtrunk circuit or via any one of said trunk circuits, means controlled by the attendant for permitting her to tallx to the main exchange over the trunk circuit over which said signal is operated, and individual means for each of said trunk circuits for. indicating the particular trunk circuit over which said signal means is operated. o 19. A telephone system including a main exchange and an executivcs substation, a trunk circuit forginterconnecting said substation and said main exchange, a private secretary's telephone set associated with said trunk circuit, means for said trunk circuit for permitting the private secretary to attend to the calls extended from said main exchange and to extend the same to said executives substation, automatic means controlled by the party atsa id substation for disassociating said substation and said main exchange and for signalling for a disconnection at themain exchange, and meansfor said link circuit for permitting said substation to receive and to extend calls between said substation and said main exchange exclusive of the private secretary.

20. A telephone system including a main exchange, and an executives substation, a trunk circuit for interconnecting the sanie, a private secre'tarys telephone set associated with said triink circuit, a trunk circuit for interconnecting said telephone set and said main exchange, signal means for said secondtrun'k circuit for signalling the prirate secretary, said means contiolied from the main exchange over said first trunk citcuitor controlled directly over said second trunk circuit, means whereby the private secretarymay receive calls over any of the trunk circuits, and means whereby she is prevented from extending calls to the main exchange over any trunk cir-ui't other than her own. y i,

Si ned by me at Chicago, county off Cook and tate of Illinois, this 15th day of May,

DANIEL B. nonisoa. 

